Fix TestFailuresPlugin.TestFailure.compareTo()

This commit also polishes around it a bit.

See gh-19863

buildSrc/src/main/java/org/springframework/boot/build/testing/TestFailuresPlugin.java

@@ -56,7 +56,7 @@ public class TestFailuresPlugin implements Plugin<Project> {
 
 	private final class FailureRecordingTestListener implements TestListener {
 
-		private List<TestFailure> failures = new ArrayList<>();
+		private final List<TestFailure> failures = new ArrayList<>();
 
 		private final TestResultsExtension testResults;
 
@@ -106,7 +106,7 @@ public class TestFailuresPlugin implements Plugin<Project> {
 		public int compareTo(TestFailure other) {
 			int comparison = this.descriptor.getClassName().compareTo(other.descriptor.getClassName());
 			if (comparison == 0) {
-				comparison = this.descriptor.getName().compareTo(other.descriptor.getClassName());
+				comparison = this.descriptor.getName().compareTo(other.descriptor.getName());
 			}
 			return comparison;
 		}

buildSrc/src/test/java/org/springframework/boot/build/testing/TestFailuresPluginIntegrationTests.java

@@ -22,9 +22,9 @@ import java.io.FileWriter;
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.io.StringReader;
-import java.util.ArrayList;
 import java.util.List;
 import java.util.function.Consumer;
+import java.util.stream.Collectors;
 
 import org.gradle.testkit.runner.BuildResult;
 import org.gradle.testkit.runner.GradleRunner;
@@ -169,17 +169,12 @@ class TestFailuresPluginIntegrationTests {
 	}
 
 	private List<String> readLines(String output) {
-		List<String> lines = new ArrayList<>();
 		try (BufferedReader reader = new BufferedReader(new StringReader(output))) {
-			String line;
-			while ((line = reader.readLine()) != null) {
-				lines.add(line);
-			}
+			return reader.lines().collect(Collectors.toList());
 		}
 		catch (IOException ex) {
 			throw new RuntimeException(ex);
 		}
-		return lines;
 	}
 
 }